The present invention relates a string trimmer and in particular to a mechanism for storing spare cutting line on a string trimmer and, more in particular, to a string trimmer using individual pieces of line which are attached to the cutting head
String trimmers are portable hand-held outdoor gardening power tools used for cutting soft vegetation, having an electrical motor or a small combustion engine, which rotatingly drives a cutting element. Typically, the cutting element comprises a hub, called a cutting head, and a cutting member attached to and extending radially from the cutting head. A cutting member may take many different forms, like for example, a blade or a filament, formed of a resilient or rigid material and, which may be permanently or detachably fixed to the cutting head. The cutting member is rotatably driven at a speed sufficiently high so that it shears any grass or soft vegetation in its path.
String trimmers can be easily manoeuvred close to vegetation in areas which are inaccessible to a conventional lawn mower or other cutting devices. However, during use the rotating cutting line comes into contact with not only soft vegetation, but also hard objects like, for example, rocks and stones. These hard objects can damage or break the cutting line resulting in the need for frequent replacement of the cutting line during use of the string trimmer.
Some cutting heads have an automatic feed mechanism comprising a reserve of cutting line wound around a spool which is mounted within the cutting head. In use, when the cutting line breaks, the automatic feed mechanism allows the spool to rotate relative to the cutting head, thereby paying out additional cutting line to compensate for the shortening of the working cutting line due to breakage or wear. A cutting head comprising an automatic feed mechanism may be convenient to use but it is also complicated to assemble and expensive to manufacture. Other cutting heads comprise a more simple and inexpensive attachment mechanism for detachably securing a single length of cutting line. Replacement of a worn or broken cutting line requires the user to stop the operation of the string trimmer, wait until the rotation of the cutting head has ceased and replace the old cutting line with a new one. Replacement of the single cutting line is a quick and simple process if the user has spare lengths of cutting line at hand.
During extended or heavy-duty trimming operations, it is possible that the cutting line is exposed to a lot of wear and may need to be replaced several times before completion of the task. Replacement of a cutting line is not an unduly inconvenient task but it may become so if the user does not have spare lengths of cutting line at hand and needs to return to the garden shed or other place of storage. Continual stopping of the task to fetch spare cutting line will soon become a major irritation to the user. A seasoned string trimmer user may carry spare cutting line in his pocket as a precaution against this problem however this is not ideal since it may lead to damage of the spare cutting lines like, for example, when the user sits down. Furthermore the spare cutting lines carried by the user may become lost.
Accordingly, there is provided a string trimmer comprising a body wherein a cavity is formed within the body and which is adapted to store at least one cutting member for the string trimmer. The body of a string trimmer may comprise at least one handle, a shaft, a motor housing and a protection guard. The cavity may be formed by a member attached to the body of the string trimmer. Alternatively, the cavity may be formed by a cavity wall formed within the body of the string trimmer. The advantage of storing spare cutting lines in a cavity formed within the body of the string trimmer is that these cutting lines are stored together in one location which is immediately accessible to the user of the string trimmer.
Though the cavity can be formed within a handle, the motor housing or the protection guard of such a string trimmer, ideally the cavity is formed within the elongate shaft of the body so that the user has easy access to the cavity.
In some constructions of string trimmer the body may be formed by an elongate metal shaft with a separate handle at one end and a motor housing at the other. Attached to the motor housing is a protection guard. A motor is mounted within the motor housing which rotatingly drives a cutting head. In such a construction, the cavity may be formed in the handle, the motor housing, the protection guard or, the metal shaft. In an alternative construction of string trimmer the body is formed by at least two moulded clam-shells, the cavity being formed by a cavity wall integrally moulded into at least one clam-shell. A clam-shell is a rigid shell, moulded in a metal or, more commonly, plastics material. The shell can be reinforced by cross members on its inner skin. The body of a string trimmer made of two clam-shells which together form a rear handle, an elongate shaft, a motor housing and, in some designs, a front handle, has the advantage of being lighter and cheaper to manufacture than a string trimmer having an elongate metal shaft with a separate handle and motor housing. A cavity wall moulded into one or both of the clam-shells would form an integral part of the clam-shell thus obviating the need to manufacture and attach an additional component to form the cavity wall. One less component provides the advantage of a reduced overall cost in manufacturing a string trimmer.
Preferably, one part of the cavity wall is integrally moulded into the first clam-shell and the other part of the cavity wall is integrally moulded into the second clam-shell in substantially symmetrical fashion, the complete cavity wall being formed when the first clam-shell and the second clam-shell are joined together. A cavity wall moulded in two halves is easier and cheaper to manufacture than a cavity wall moulded in one piece.
Preferably the cavity wall forms a tubular passage having at least one aperture through which a cutting member is capable of being inserted into the tubular passage A tubular passage can be understood to mean an elongate cavity. Either one end or both ends of the tubular passage may be sealed. The length of the tubular passage may be appreciably greater than its breadth. The tubular passage can be sufficiently broad and long to fully enclose one or several cutting lines at the same time. The aperture may be formed in one end of the tubular passage. Alternatively, the aperture may be formed in a side wall of the tubular passage. In either case, if the aperture is located towards the upper end of the tubular passage then a cutting line is held within the tubular passage due to the force of gravity.
Preferably, the shape of the tubular passage is configured such that the cavity wall interacts with a cutting member when a cutting member is located within the tubular passage to secure a cutting member within the tubular passage. This interaction may be, for example, due to a distortion, a constriction or a locking mechanism comprised within the cavity wall, any one of which may be adapted to secure a cutting line once it is located within the tubular passage.
Preferably the tubular passage is curved along its length. This provides the benefit that when a substantially straight resilient cutting member is located within the tubular passage the cavity wall causes a cutting member to bend, frictionally engaging the cavity wall of the tubular passage, thus holding a cutting member in the tubular passage. The curvature of the tubular passage can be constructed so that, when a substantially straight resilient cutting member is inserted into the curved tubular passage, it is forced to make contact with the cavity wall at a number of contact points. One such type of resilient cutting member is a cutting line. When a cutting line is inserted into the curved tubular passage a cutting line bends in order to fit the path formed by the tubular passage. The resilient nature of a cutting line causes it to frictionally engage with the cavity wall at various contact points, the forces required to overcome the friction being sufficient to hold a cutting line within the curved tubular passage. The advantage of a curved tubular passage is that the interaction between a cutting member and the cavity wall provides for a simple and inexpensive mechanism of securing a cutting member within the curved tubular passage.
Preferably the cavity wall of the tubular passage comprises a first straight tubular section at one end, an intermediate curved tubular section where the cavity wall forms a xe2x80x98vxe2x80x99 shape kink, and a second straight tubular section at the other end, the first and second straight tubular sections being substantially co-axial. The xe2x80x98vxe2x80x99 shaped kink frustrates a straight path through the tubular passage. When a substantially straight resilient cutting member is located in the tubular passage it is forced to make contact with the cavity wall at a number of contact points in the region of the xe2x80x98vxe2x80x99 shaped kink and is resiliently deformed by the cavity wall in order to fit the path formed by the xe2x80x98vxe2x80x99 shaped kink. The resilient nature of a cutting member causes it to frictionally engage with the cavity wall at various contact points, the forces required to overcome the friction being sufficient to hold a cutting member in the tubular passage. A feature of the tubular passage comprising an intermediate section where the cavity wall forms a xe2x80x98vxe2x80x99 shaped kink is that the cross-sectional area of the tubular passage can remain substantially the same throughout the first straight, intermediate and second straight tubular sections and is therefore formed without a bottleneck. The absence of any bottlenecks in the tubular passage provides the advantage of maximising the number of cutting members that can be inserted into the pouch.
Preferably a lip is formed adjacent to the aperture, the lip being adapted to retain a cutting member within the tubular passage. The lip can be formed between one end of the tubular passage and the aperture. The lip can enclose the end of a cutting member closest to the aperture when the cutting member is located within the tubular passage. To fully locate a cutting member within the tubular passage one end of the cutting member is inserted through the aperture and moved towards the lower end of the tubular passage. The other end of the cutting member remains out side the tubular passage until the cutting member is deformed so that its other end clears the overhang of the lip, passes through the aperture and locates itself behind the lip and inside the upper end of the tubular passage. A cutting member will not deform and undo the above sequence without intervention on the part of the user, therefore, the enclosure of both ends of a cutting member by the tubular passage and the lip will result in the cutting member being retained. The function of the lip can provide an additional or alternative, simple and inexpensive mechanism of retaining a cutting member within the tubular passage.
Furthermore, if a cutting member is not substantially straight and is instead similar in shape to the xe2x80x98vxe2x80x99 shaped kink of the tubular passage then frictional contact between the cutting member and a cavity wall may not occur. In this case the xe2x80x98vxe2x80x99 shaped kink of the tubular passage may not retain the cutting member and the lip may be the only mechanism retaining the cutting member within the tubular passage.
Preferably, the aperture is located away from an extremity of the tubular passage, such that the portion of the cavity wall located in between the aperture and the extremity forms the lip. An extremity of the tubular passage is understood to mean an end which terminates the tubular passage. A lip moulded into part of the cavity wall obviates the need to manufacture an additional component forming the lip. One less component provides the advantage of a reduced overall cost in manufacturing a string trimmer.